Exoplanet science with intensity interferometry

While the transit method has been a fruitful technique for detecting exoplanets, it is not suited for spatially resolving their features. The largest exoplanets detected have angular sizes of <0.1 mas, far below the spatial resolution limits of modern telescopes. Some transiting hot Jupiters show evidence of lopsided structures on scales of order 10 μas: asymmetric atmospheric molecular abundances and very strong zonal winds reaching up to orders of ~10km/s. Imaging such features is beyond the limits of conventional imaging techniques. However, intensity interferometry, a technique that involves spatially cross-correlating the photons from pairs of telescopes, offers the prospect of angular resolution on such scales at optical wavelengths. In the optical band around wavelengths of 350 nm, it can achieve resolutions of <10 μas, in the near-infrared band around wavelengths of 1050 nm, it can achieve resolutions of <30 μas, with a telescope baseline of 5km. Suggestively, the former range overlaps with the iron absorption lines in WASP-76b, a hot-Jupiter that has an asymmetric atmospheric iron abundance. The latter overlaps with the He I triplet line in HD 189733b, a hot-Jupiter that has an evaporating atmosphere. We explore the prospects of detecting such hot-Jupiter features using various telescope combinations like the next-generation atmospheric Cherenkov telescopes, the Very Large Telescope (VLT) and the Extremely Large Telescope (ELT). We calculate the interferometric signal from the above exoplanets and their asymmetric atmospheric features using these setups.